Coherently Coupled Soliton Pairs In Two-photon Photorefractive Media

Photorefractive spatial solitons due to the microwatt dimension of light intensity, and the character of strong nonlinear effect, have a wide application prospect in optical interconnection, optical integration, optical waveguide and optical switch and many other aspects, becoming one of the important research topics in nonlinear optical field nearly 20 years.This article focus on the theoretical study of two coherently coupled beams propagating in the same line in two-photon photorefractive media. Firstly, we propose the coherently coupled equation of two beams along the same straight line propagation of soliton beam with the external electric field and neglecting the diffusion in two-photon photorefractive media from the model of Castro-Camus. The solution of the equation is obtained by the integral form of coherently coupled bright-bright soliton pairs, dark-dark soliton pairs and gray-gray soliton pairs, and the required conditions of the coherently coupled bright-bright, dark-dark soliton pairs and gray-gray soliton pairs in the two-photon photorefractive crystals are also obtained. And we discuss the influence of external electric field and the initial phase difference. Numerical simulation is carried out with Cu: KNSBNcrystal and Li Nb O3 crystal as an example.The dynamics equations of two beams traveling in the same line in two-photon photovoltaic photorefractive media are given, we discuss the required conditions of the bright-bright, dark–dark and gray-gray soliton pairs, and also the influence of initial phase difference and other factors of each configuration soliton pairs. As an example, numerical simulation of Cu:KNSBN crystal and Li Nb O3 crystal is carried out.We present the propagation of two solitons in two-photon photorefractive medium with diffusion effect, and the coupled wave equation is given. We get coherently coupled bright-bright soliton pairs in two-photon photorefractive media, and give the lateral offset of soliton center and the offset of angle in the diffusion effect, and make numerical simulations to prove the theory. Finally, the self steering effect of the coherently coupled shield is considered for the small amplitude case, and the analytical solution is obtained.